A semiconductor device such as an LED or a power module has a structure in which a semiconductor element is bonded onto a circuit layer formed of a conductive material.
A power semiconductor element for controlling a high amount of power used to control a wind power generation system or an electric vehicle such as an electric automobile generates a large amount of heat. For this reason, a ceramic substrate having good heat resistance and good insulating properties, which is made of silicon nitride (Si3N4), aluminum nitride (AlN), alumina (Al2O3), or the like, is used as a substrate on which such a power semiconductor element is mounted. In the related art, a power module substrate, in which a high-conductivity metal plate which is a circuit layer is bonded to a first surface of the ceramic substrate, is widely used. Another metal plate may be bonded to a second surface of the ceramic substrate.
For example, a power module substrate disclosed in Patent Document 1 has a structure in which a circuit layer is formed by bonding a Cu plate (Cu member) to a first surface of a ceramic substrate (ceramic member). In the power module substrate, the Cu plate is bonded to the first surface of the ceramic substrate by heating the Cu plate and the ceramic substrate in a state where the Cu plate is disposed on the first surface of the ceramic substrate with a Cu—Mg—Ti brazing material interposed between the ceramic substrate and the Cu plate.